It is known from British Pat. No. 1,195,761 to Wacker-Chemie that organohalosilicon compounds can be prepared by reacting halosilicon compounds with organosiloxanes which are free of Si-bonded halogen in the presence of phosphonitrile chloride. According to the teachings of the British patent, substantially greater amounts of halosilicon compounds and phosphonitrile chloride were employed than is employed in the present invention. Moreover, the British patent does not describe the preparation of diorganopolysiloxanes having terminal Si-bonded hydroxyl groups. Furthermore, the British patent does not describe a process for controlling the viscosity and molecular weight distribution of the diorganopolysiloxanes.
Therefore, it is an object of the present invention to provide a process for preparing diorganopolysiloxanes containing terminal Si-bonded hydroxyl groups, in which the viscosity of these diorganopolysiloxanes can be controlled. Another object of the present invention is to provide a process for preparing diorganopolysiloxanes having terminal Si-bonded hydroxyl groups from readily available organosilicon compounds in good yields. A further object of the present invention is to provide a process for preparing diorganopolysiloxanes having terminal Si-bonded hydroxyl groups having a narrow molecular weight distribution.